1.1: sodium hydride / tetrahydrofuran / 0.25 h / -10 °C 1.2: 2 h / -10 °C 2.1: lithium borohydride / tetrahydrofuran / 1 h / 20 °C 3.1: dimethyl sulfoxide / 72 h / 20 - 70 °C 4.1: phosphoric acid; water / methanol / 24 h / 20 °C View Scheme